Signaling system



June 11, 1940.

M. GEIGER SIGHALING SYSTEM Filed Feb. 20, 19 7 2 Shgetsv-Sheet 1 lNvEN-roR MAX GEIGER BY M ATTORNEY Patented June 11, 1940 SIGNALING SYSTEM Max Geiger, Berlin, Germany, assignor to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, Germany, a corporation oi Germany Application February zo, 1937, Aserial No. 126,783 In Germany February Z5, 1936 6 Claims.-

This invention relates to signaling systems, and in particular, interlaced scanning systems such as used in television, for example, it is accordingly the purpose of this invention to provide a new method and means for producing improved interlaced scanning in television signaling sysems.

Turning to the drawings, in which Figs. l. through 6 show graphically the array of line and framing synchronizing impulse sequences useful to explain the operationof my invention; and

Fig..7 shows in block diagram form the apparatus for producing the interlaced synchroniz` ing system embodied in my invention; l will describe the invention in more detail below.

For the transmission'of television pictures it has been suggested in the prior art to use an interlaced or skip-line method in such a way` that each line series or sequenceA (or partial scan) would consist of a fractional number of frame or picture lines, so that the complete picture to be televised would be entirely transmitted only by a plurality of such line sequences or partial scans. The time-base of the line impulses (horizontal impulses) vand the linesequence impulses (vertical impulses) is shown -in Fig. 1 for the simple instance where the entire frame or picture is to comprise merely 2l lines or strips, and where the whole trame is to be transmitted by merely two partial scans of line-sequences. In the said iigure, the horizontal impulses are designated by H and the line-sequence impulses by V. Each of the line sequences has the same periodicity of 10i/2 line lengths. The fact that in this method quantity d, that is, the time interval between a line sequence impulse V and the respective preceding line impulse H differs for each line sequence constitutes a serious drawbackfor the reason that customary practice is to transmit the impulses H and V with like amplitude, and that the impulses V must be separatedfrom the impulses H by the aid oi i'requency selector or filters. Now, the said irequency filter means, upon the first line sequence or partial scan for which quantity d is always equal to a full-line length is ina state diierent from that in the next partiafscan er line sequence `for which quantity d amounts to only V2 a line. The result is that, even if the line sequence impulses V are perfectly equal to one another, the frequency selector means will react or respond dlssimilarly in both instances, with the consequence that the lines of one sequence or partial scan will `not come to fall exactly into the spaces or intervals of the `respective other (Cl. ri-69.5)

partial scan, and this is extremely annoying when viewing the incoming picture. ln order to more clearly-understand what follows, it must also be noted that quantity D which stands for the time interval between the beginning of a linesequence impulse and the nrst line impulse of thevnext line sequence or partial scan difiers in size for each line sequence in the before-men" tioned method. To summarize, the values oi d and of D are of dissimilar values for each'par tial scan.

In order to obviate the dimculties due to such diiierence in operation of the frequency selector filter means which is caused by the variability of quantity d, an interlaced-scanning method has been suggested in the earlier art in which quantity d for each line sequence is equally great, While quantity D for each line sequence is also ci the same value (see copending application Ser. No. 124,9?"1, for a Sawtooth generator, filed Feb. il), 1937, by Robert Andrieu). The time representation of the shape of the line impulses H and the sequence impulses V forthis last-named method according to Fig. 1 is illustrated in lllg. 2. The two line sequences contain dissimilar numbers oi line lengths, i. e., 11 and itl. lines, assuming again a television frame comprising 2l lines only, Quan tity d in this instance is the same ier each line sequence, and accordingly the frequency selection diiliculties are absent in this method. Also quantity D is the same foreach partial scan. But the iirst line sequence er partial scan of each frame, contradistinct to the method illustrated in Fig. 1, is no longer of the come duration as in the second partial scan.` However, in practicing this methodit ia necessary at the re ceivlng end that the saw-tooth generator for the vertical deectlon should be so designed 'that upon each sequence impulse it should return the same amount, regardless of the number of lines contained in the previous partial scan or line se quence. The initial position oi the cathodewray pencil building up and delineating the incoming picture, as will thus be noted, is not the same for each partial scan inasmuch as the duration of the various line sequences is different, and since the distance which the pencil is to skip back after completion of each partial scan must in each instance be the same as indicated. New, a saw-tooth generator which in one impulse, regardless'of the state of deflection of the cathoderay pencil prevailing at a given time will always return the same distancais not quite so simple in :lts construction as the .usual sawtooth oscilpractice in which a condenser is charged up by way of a resistance from a D. C. source of supply, while upon the arrival of the sequence impulse a thyratron connected in parallel relation to the condenser is ignited. It will be remembered that the discharge of a thyratron is caused vtodiscontinue only when the condenserhas been discharged to the same fixed voltage. On the contrary, in the method covered by Fig. 2 a circuit scheme must be used in which the condenser, independently of the potential to which it has been 4charged up 'in the course of a partial scan `will in each case yield the same quantity of electricity. This condition may be satisied, 'for example, by the aidof a high=vacuum tube connected in what is known as the blocking-oscillator circuit organization. What is meant by this is a regenerative tube in which the coupling between the plate and the grid circuits isv made extremely close, and in which, uponl the arrival ofV an impulse at the grid, a brief. but powerful current is caused to flow. in the plate circuit which reduces the grid potential to a value away below the lower bend of the grid-plate (mutual) characteristic whence the grid potential'will rise again in a. gradual way until the time of incipient flow of plate current which is initiated by the next impulse. Hence, what is a typical fact for the interlaced-scan method according to i Fig. 2 is that the values of d and Dior each partial scan or line sequence are alike.

Now, according to the present invention the values of d foreach line sequence or partial scanl when working in accordance with the present invention, the condenser. of the vertical saw-tooth oscillator can again be discharged across 'a thyra tron tube.

Fig. 3 shows the' impulse sequence. It will become clear therefrom that the line sequence impulse, in each partial scan, presents the same distance from the preceding line-sequence impulse, with the Vresult that dimculties previously attendant upon filtering are precluded. Moreover, the timeinterval between the initiation of a line-sequence impulse and the following line impulse'diifers for each partial scan of the frame. The line sequences, just as in the method indicated in Fig. 2, though contradistinct to the method covered by Fig. 1, comprise a diil'erent number of line lengths, namely, lOl/2 and V11 lines. But the number of lines per frame, contredistinct tothe methods according to Figs. 1 and 2, is a fractional number.

By reference to Figs. 4 and 5 there shall i'lrst be explained the building up of a. frame or picture. in the case of Fig. d, the horizontalv co-ordinate stands for the time, and the vertical co-ordinate for the` vertical direction in the television frame..

The times between the incipient line-sequence impulse and the beginning of the vertical deection for the next partial scan is here assumed to be equal to two line lengths. At the instant ti when Sequence.

a partial-scan impulse starts, the saw-tooth oscillator begins to run beck so that at instant t:

it has been restored to its initial state. Then thel vertical deflection starts in the course' of which lines l to 'l of the first line sequence are delineated (traced). A distance equal to one line length from the seventh -line impulse, that is to say, at instant t3, another partial-scan impulse starts, and at time ti which again is two lines away from time t3, the vertical deection for the second partial scan commences. The line impulses of the said second sequence occur at such instants that the lines of the second partial scan come to lie between the lines making 'up the iirst line Again seven lines are delineated, and these, as stated, nl] up the spaces left by the first partial scan. At instant t5, following the seventh line impulse of the second partial scan, there is provided again a new sequence impulse, spaced one line apart, which initiates a new line sequence whose lines come to. coincide or register with those of the inst-mentioned line sequence or partial scan (between t2 and ta) In Fig/5 the lines of the partial scan occurring between times ta and t3 are indicated solid, while the lines between t4 and t5 vare represented dotted.

The-method here disclosed, like the methods according to Figs. 1 and 2, is useful not only in the case of two partial scans per frame but also in cases where the partial scans or subdivisions of a frame amount to three, four or more interlacings.

In the general, instance where n: many line sequences o r partial scans exist per picture, there holds then true:A l

d constant Y nl D=p, :i+1/n, :J+2/n 7D+-.n Whre d and i may be of any desired size. In the method covered by Fig. 3, d=1 and p=3/2.

Before the production of the impulse sequences in a method according to this invention, is discussed by reference to Figs. 6 and 7, the fact is to,4

be emphasized that in the new method'here disclosed, as follows from Fig. 3 any two .line impulses, inside the first frame, present an integral time distancemeasured in terms of line lengths, whereas the distance between any desired line impulse of the' frame and any random line impulse of the second one is not an integer. Ap-

plied to the general case where d=constant and D=p+l/n, :J+2/u, etc. the said rule reads as follows: Inside the first picture, any two line impulses present a distance between each other (expressed in terms of line lengths)l which, when divided by the line length, leaves a diderent remainder than the time interval between any given impulse of the iirst frame and any desired impulse of at least one of the following n-l pictures. between two random impulses-of the first and at least one of the following n-l pictures there On the other hand, for the time intervall 4 2,208,865 having the same frequency. Such phase oppo.-l l

sition may be insured for instance, in a simple manner by the .aid of a push-pull scheme in the output stageof the frequency divider. From the impulse` series l are further made two chains -IV and VI whose impulses are of a frequency twice that of the impulses `contained in sequence I, though presenting a phase .angle equal to the period of I. If, then, by the aid of the impulses of sequence II .the impulses in sequence VI are keyed (in other wordsif impulses VI are allowed to become operative when an impulse of `sequence II exists, while suppressing them during the intervals between, the impulses of sequence II), it is possible to obtain the line impulses for, the first frame. The line impulses for the second frame are produced in the same manner by keying sequence IV bythe aid of sequence III. The total impulse series which is made up 'of sequence or chain VII is obtained if to the line impulses ensuing in a way as indicated from IV and VI, verti'- cal impulses are added, say, in a fashion described in the co-pending patent application Ser. No. 124,977,referred`to above. I

A schematic representation of the circuit organization required to produce vthe impulse mixture is shown in Fig. 7. 20 denotes the impulse generator for sequence I. It feeds a frequency divider 2l with a push-pull output stage which by Way of Wires 22 and 23 furnishes the impulse series II- and III. 24 and 25 denotetwo impulse generators which may consist of multi vibrators Ihaving a frequency half the natural frequency of chain I, the said impulse generators being designed to be connected and disconnected by way of the leads 26, 21, that is, impulse chains IV and VI. In a suitable device, say, a mixer hexode 28, there is brought about the combination of the line impulses for the first and for the second frame, and on the line 29 there arises the horizontal impulse mixture or spectrum so that the lead 3l will deliver the impulse chain VII.

The impulse generatorr20, for example, may take the form shown in Fig. 2 of U. S. Patent y No. 1,802,745, issued April 28, 1931, to James N. Whitaker for "Dot multiplex and the multivibrators 24 and 25 may be of the form described in the paper entitled A convenient method for referring secondary frequency standards to a standard time interval" by Hull and Clapp in the Proceedings of the `Institute of Radio Engineers, for February 1929, beginning at page 252 et seq. and in particulanat page 258, or. in the paper entitled Universal frequency of standardization from a single frequency standard by J. K. Clapp, which appeared in the Journal of `the Optical Society of America, volume 15, 1927, atV

page 25. i

Having described my invention, what I claim is:

l. A synchronizing system comprising. an impulse generator, a push-pull amplifier, means to feed energy .from the impulse generator to the push-pull l amplifier. a -plurality of multivibrators, means to feed energy'from both the impulse generator and the push-pull amplifier to each ofthe plurality of multi-vibrators, and means to derive energy from each of the multivibrators and means to combine the derived energies. l

2. A synchronizing system comprising an impulse generator, apush-pull amplifier, means to feed energy from-the impulse generator to the push-pull amplifier, a plurality of multivibrators, Ameans to feed energy from both the impulse generator and the push-pull amplifier to each 'of the plurality of multi-vibrators, means to derive energy from each of the multivibrators, means to combine the derived energies. and means to transmit the combined ences.`

3. A synchronizing system comprising an impulse, generator, a push-pull amplifier, means to feed energy from the impulse generator to the push-pull amplifier, a plurality of multi-vibrators. means to feed energy from both the impulse gen erator and the push-pull amplifier to each of the plurality of. multi-vibrators, Ameans to derive energy from each of the multi-vibrators, means to combine the derived energies, means to transm mit the combined energies, means to combine,

the combine'd energies with picture signals, and means to `transmit the vcombined lastnamed combined energies.

4.'The method Aofinterlacing in a television system which comprises scanning aportion of a picture area over a predetermined number of integer line paths, and scanning the remainder of said picture area over a non-integer number of line paths, said first and second named paths alternating with each other.

5. The method of interlacing in a television systemwhich comprises scanning a portion of a picture area over a predetermined number of integer line paths, and scanning the remainder of said picture area over a number of paths dif fering from said predetermined number of paths by a. fractional amount of one path, said first and second named paths alternating with each other.

6. The method of interlacing in a televisioni system which comprises scanning a portion of a picture area over a predetermined number of 

